Conventional digital cameras can simply capture and input image information. The image information should be further processed by a general purpose computer and then transferred to a peripheral apparatus or transferred from the peripheral apparatus into the computer and then processed. As calculation capability of the computer is enhanced increasingly, an advanced digital camera is provided to take a photo image, digitalize the image and store the digital image. In addition, the digital camera may have a function of taking a motion picture. The motion image information is converted to a video format to be filed or played. Thus, the digital camera can create the video information except for the image information.
As information technology is rapidly developing, the digital camera has already become a hot digital product in the past few years. The image information can be directly input into a general-purpose computer without using conventional film, The image information may be edited in the computer to operate in coordination with the popular application of the Internet. Further, the semiconductor technology is enhanced continuously, causing the production cost to decrease continuously. The functions of the digital camera are newly and variously designed; consequently more and more people expect to have a digital camera. A motion detection function is especially distinctive for the digital camera.
The digital camera essentially includes four units as schematically shown in FIG. 1. An image sensor 102 receives an optical image signal, which is further converted to digital image information. A lens unit 101 is used to form an image on the image sensor 102. A control device 103 is used for controlling all units in the digital camera to input/output image information or further process the image information. A storage device is used for storing the digital image information. The optical image signal of an object is formed through the lens unit 101 on a light sensitive surface of the image sensor 102. The control device 103 controls the image sensor 102 to convert the optical image signal to digital image information. The digital image information is further transferred to the control device 101 or directly to the storage device 104 if the digital image information will not be further processed. The storage device 104 can be a nonvolatile memory, such as EEPROM, Flash, or a volatile memory, such as DRAM, SRAM. The control device 103 processes or determines the image information form the image sensor 102 and controls actions of all elements or units and coordinating operation between the units.
A motion detection function has been available for quite some time. However, some prior art detecting motion methods have employed expensive external apparatus, such as infrared or microwave motion detector devices, and a computer with mass calculation capability. Since the conventional method of detecting motion utilizes a complicated mathematical algorithm, the original microprocessor of the control device of the digital camera is not burdened with the extra functions for detecting motion. The microprocessor should be replaced by one with a mass process capability, but this increases the cost of the digital camera. Besides, the conventional method of detecting motion needs a large capacity memory and a lot of time to detect motion. Comparing with the above-mentioned conventional method, the present invention has an advantage of a simple mathematical algorithm. Therefore, a need exists to provide a method of detecting motion for digital cameras to solve the problems of the conventional detecting method.